Modular building unit and method of assembly

ABSTRACT

The invention provides a modular building unit comprising a shell formed from side wall lattice frameworks connected together by cross-beams at floor and ceiling height and end wall lattice frameworks secured to the ends of the resulting structure. The wall lattice frameworks are constructed at a first site where each is formed from an array of mutually parallel spaced structural uprights made from cold-formed structural steel sections, secured together by horizontal or diagonal cross-braces also made from cold-formed structural steel sections. The wall lattice frameworks are build up into the shell at a second site where each of the cross-beams, made from a cold-formed structural steel C-section, is connected to the wall lattice frameworks by being sleeved into or around lateral spur members extending from the wall lattice frameworks prior to being welded thereto.

The invention relates to modular building units for use in theconstruction of largely prefabricated offices, hotels and apartmentblocks, and buildings of a similar general nature. Such modular buildingunits are box-like structures which can be manufactured and fitted-outoff-site and then transported to a construction site for final assemblyto form the internal rooms of a building.

BACKGROUND ART

Particularly in the construction of hotels, apartments and studentaccommodation it is known to construct the buildings from lightweightbuilding modules each of which is a skeletal steel shell formed fromlightweight structural steel sections welded into a box-like structureand lined with boarding such as plasterboard, plywood or oriented strandboard (OSB). Each building module is made initially as such a linedshell, and is then fitted-out to the desired standard of internaldecoration in a factory before being transported to the final buildingsite for incorporation into a building.

GB-A-2334045 discloses one method of construction of such a buildingmodule. A number of rectangular or otherwise identically shaped framemembers are formed and aligned in mutually spaced parallel relationshipas the ribs of the final skeletal shell. Then they are connectedtogether by multiple cross-braces which lie on the inside of theresulting shell. Wall panels are secured to the cross-braces. Floor andceiling panels are added, as are end panels, and the module is finishedto its final standard of internal decoration.

One inevitable characteristic of the module of GB-A-2334045 is that theentire module is made and fitted-out in a single factory. The initialfabrication step of setting out the pre-formed row of rectangular framemembers and joining them together with the horizontal cross-bracescreates a skeletal steel box-like structure. Once this skeleton iswelded into its final box-like shape or shell the transportation of thatshell becomes a major expense, with a separate lorry or low-loader beingneeded to move each such skeletal shell out of the factory. Thereforethe shells are lined and fitted out in the same premises which may be aconsiderable distance from the site of the final building to be erected.The completely fitted-out modules are then transported, generally byroad, to the final building site for erection of the hotel or apartmentblock to be built. This carries with it considerable potential transportcosts.

Another characteristic of the module of GB-A-2334045 is that a directthermal path is provided from the internal panelling to the framemembers through the cross-braces. A fire in the finished buildingtherefore has a relatively short heat path before it causes distortionof the ribs or frame members which are the structural uprights of thefinished building. This is a major concern because the steel of theframe members and cross-braces is lightweight steel framing and canreadily distort in the event of thermal overload. The maximum height ofa building made from modules in accordance with GB-A-2334045 istherefore a relatively small number of storeys, typically about four orfive.

It is an object of the invention to provide a building module and amethod of building using such modules which both reduces cost andimproves the fire resistance of the building as compared with the use ofsimilar grade materials in the known modular building methods. Byimproving the fire resistance of each module the invention permits theerection of higher rise blocks of rooms using the building modules ofthe invention.

The Invention

The invention comprises a modular building unit as specified in claims 1to 11 herein, and a method of fabricating a modular building unit asspecified in claim 12 herein.

The building modules according to the invention can be stacked in ahorizontal and vertical array using edge location means as described andclaimed in copending Patent Application No W068005 filed herewith, andlinked together horizontally and vertically as described and claimed inW068006 filed herewith, to form buildings 20 or more storeys high. Ifdesired the outside of such buildings can be cross-braced using diagonalstructural members which may themselves be made from lightweightcold-formed steel section. Such cross-braces are known per se. That mayhowever be unnecessary if the cross-braces are located diagonally ratherthan horizontally.

The lightweight structural steel sections used as the structuraluprights in the modular building units of the invention have excellenttensile stress resistance but relatively poor compression resistance.Additional tensile stress resistance may however be provided byincorporating a rod or tube or cable within selected ones of thestructural uprights. If rods or tubes are used, then each preferablyextends the full height of the wall lattice framework, which is theheight of one full storey of the erected building, and preferablyterminates at each of its ends with means for connecting that rod ortube to aligned rods or tubes of the vertically adjacent storeys. Thateffectively ties together the successive storeys of the finishedbuilding in the vertical direction. If desired similar rod, tube orcable reinforcement can extend horizontally from end to end or side toside of the building module through the wall lattice framework orthrough the cross-beams, for tying together adjacent modules of theerected building in the horizontal plane.

Particularly for the construction of buildings more Man 20 storeys high,or buildings that are susceptible to lateral shear forces caused by sidewinds, the external walls of the buildings are preferably reinforced byhighly compression-resistant columns either included within the wallthickness of the pre-formed rectangular frame units or secured to theoutsides of the individual modules or stacks of modules.

A preferred form of compression-resistant column is one which comprisesa hollow tubular steel section filled with concrete, preferably withconcrete that is reinforced with steel rods. The steel section may behot-formed, for example as rectangular or circular section tubular steelstock, or may be made from lightweight cold-formed steel similar to thesteel used in the remainder of the building module. Individualcompression-resistant columns may be the height of one single modularbuilding unit or may be the height of two or more storeys in the finalbuilding. If the former then the compression-resistant columns may beincorporated into the individual wall lattice frameworks. Otherwise theymay be attached to the outside of the assembled building module or tothe outside of the assembled building. If desired thecompression-resistant columns may be pre-cast and optionally reinforcedconcrete columns each of which is received in a void established betweentwo or more mutually spaced parallel structural uprights, and the walllattice framework built around those columns.

The invention also provides a method of fabricating the modular buildingunit of the invention when divided in a cost-effective manner betweentwo manufacturing sites as specified in claim 17 herein. The side andend wall lattice frameworks are made and assembled at the first site,and also at the first site it will generally be convenient tomanufacture all other cold-formed metalwork, including the cross-beamsand any other formed metalwork to be used in the final assembly process.This means that all of the apparatus for cold-forming the structuralmembers from lightweight steel can be provided at that first site. Also,the assembly of the wall lattice frameworks, which is a skilledoperation requiring a high degree of precision, is suitably carried outat that first site. The assembly of the wall lattice frameworks isgenerally achieved by placing the individual structural formed steelmembers in an assembly jig, and then welding the components together byspot welding, seam welding or plug welding. The end product of thatfirst manufacturing site is therefore a series of essentially flat walllattice frameworks and optionally a series of essentially linearstructural members such as the cross-beams, all of which can be loadedflat onto a lorry or railway truck, enabling the components of severalmodular building units to be loaded together onto a single lorry ortruck. From the first site, those components are then transported to thesecond manufacturing site, which would typically be a regional siterelatively close to the area in which the final building is to beerected from a number of assembled modules. At the second site, the walllattice frameworks are assembled with the cross-beams to form the shell,and the shell is lined and fitted-out. Movement of the shell from thesecond site does require a single lorry or low-loader to transport eachindividual building module to the final building site for erection intoa building, but by strategic use of regional assembly sites, the entireoperation can be made much more economical than the assembly method ofGB-A-2334045 which requires the assembled units to be transported from asingle manufacturing and assembly site where all of the precision workas well as the non-precision work of assembly and fitting-out isperformed.

Preferably both the structural uprights and the cross-beams are ofC-section. As is well known, such a section comprises a back face, twoside faces and two front faces. Added strength can be provided byincluding one or more swages in one or more of the back, side and frontfaces, and the strength can if desired be further increased by includingan inturned flange on one or both of the front faces. Even greaterstrength can be created by sleeving together two C-sections, one ofwhich is swaged and the other of which is unswaged or swaged in theopposite direction, so that the assembly of the two C-sections creates abox structure with one or more continuous box channels runninglongitudinally of the final composite section.

The spur members which extend from the wall lattice frameworks may beT-shaped in plan view, each comprising two limbs of which one sitsinside the C-section of the associated structural upright and the otherextends transversely therefrom as a spur to receive an end of anassociated cross-beam which is sleeved into or around that spur prior tobeing welded thereto.

The structural uprights, the cross beams and even the cross-braces arehowever preferably structural building elements formed from cold-rolledsteel with sections as described and claimed in copending PatentApplication No W068007 and as specified in claim 9 herein. Such sectionsare based generally on a C-section profile but with the maximum use oflarge diameter curves in place of the conventional flat faces. Thesesections are referred to herein as multi-curve C-section profiles.W068007 also discloses connectors suitable for joining together suchmulti-curve C-section profiled building elements into a latticeframework such as would be used according to this invention. In atypical lattice framework using only multi-curve C-section profiledstructural uprights, cross-beams and cross-braces, the cross-braceswould be in short lengths, each spanning only a single gap betweenadjacent structural uprights and connected to the structural uprights byT-connectors or K-connectors according to W068007. Alternatively thecross-braces could be wider than the structural uprights, with thelatter passing completely through oval slots stamped into thecross-braces during fabrication. Welds would be needed to secure thejoints and make the lattice framework rigid.

The cold-formed steel resilient bars which connect the wall panels tothe cross-braces are preferably Z-section profiles of which both formedangles are obtuse. One longitudinal edge portion of such a Z-section isa flange which is secured to thecross-braces, preferably down a verticalline of fixing points midway between adjacent structural uprights. Thewall panels of the internal cladding are secured to the oppositelongitudinal edge portion of the Z-section, which is also formed as anedge flange. The fixing means for the wall panels to the resilient barsmay be any convenient mounting method, such as self-tapping screws. Thetwo obtuse angles of the preferred Z-section shape provides resilienceto the mounting of the internal cladding on the interior of the shell,that resilience being sufficient to reduce the sound transmissionbetween the wall panels and the shell. Nowhere do the wall panelscontact the structural uprights or the cross-braces, because they areheld clear by the resilient bars. There is therefore no direct soundtransmission from the wall panels to the structural uprights and, muchmore importantly, an extended heat path is provided between the wallpanels and the structural uprights, passing first through the resilientbars to the cross-braces and then longitudinally of the cross-bracesbefore they in turn are connected to the structural uprights. Thisextended heat path provides excellent thermal protection for thestructural uprights in the event of a fire within the modular buildingunit. Preferably the wall panels used as internal cladding on theinterior of the shell comprise two thicknesses of plaster board for evengreater acoustic and thermal insulation.

The internal cladding to the interior of the shell also comprises floorand ceiling panels. Preferably additional external panels of floor panelthickness and strength are applied over the top of the shell. The lattermeans that when the modular building units are being assembled into abuilding, those additional external panels applied over the top of theshell can take the weight of the workforce assembling the building,without the need for scaffolding or walking boards.

DRAWINGS

FIG. 1 is a schematic illustrating the drawing convention of FIGS. 2 ato 2 e;

FIGS. 2 a and 2 b are elevations of the skeletal structures of two sidewall lattice frameworks of a modular building unit according to theinvention;

FIGS. 2 c and 2 d are elevations of the skeletal structures of two endwall lattice frameworks of the modular building unit;

FIG. 2 e is a plan view of the floor and ceiling joists of the modularbuilding unit;

FIGS. 3 to 8 are sections taken along the sectional planes 3-3 to 8-8respectively of FIGS. 2 c, 2 d and 2 b;

FIGS. 9 to 12 are enlarged sectional details of the zones indicated 9 to12 respectively of FIG. 2 e;

FIG. 13 is a plan view of a piece of sheet steel blank which is foldedto fabricate a first part of a spur member for securing the cross-beamsto the wall lattice frameworks, with the intended fold lines being shownin broken line;

FIG. 14 is a perspective view of the blank of FIG. 13 folded into itsfinal shape;

FIG. 15 is a perspective view corresponding to FIG. 14 but with areinforcing plate added;

FIG. 16 is a perspective view corresponding to FIG. 15 but with twovertical C-channels added to develop a generally T-shaped plan viewoutline to the spur member;

FIG. 17 is a perspective view of an alternative design of spur member;

FIGS. 18 a to 18 j are alternative C-sections that can be used for thestructural uprights;

FIGS. 18 k to 18 n are alternative multi-curve C-section profiles asdisclosed in W068007;

FIG. 19 illustrates the section of across-brace for use with theC-sections of FIGS. 18 a to 18 j;

FIG. 20 illustrates the section of a steel resilient bar to support thewall panels and hold them away from the structural uprights;

FIG. 21 is a vertical section through a compression-resistant column foruse in the erection of a tall building from modules according to theinvention;

FIG. 22 is a horizontal section through two structural uprightsstraddling a pre-cast reinforced concrete compression-resistant columnto be used as an alternative to that of FIG. 21; and

FIG. 23 is a side elevation of a preferred lattice framework usingstructural uprights and cross-braces with the section shown in FIG. 18k.

Referring first to FIGS. 1 and 2, the modular building unit of theinvention is made by first constructing two side wall lattice frameworksas seen in FIGS. 2 a and 2 b, and two end wall lattice frameworks asseen in FIGS. 2 c and 2 d. Each such lattice framework comprises anarray of mutually parallel spaced structural uprights 20 securedtogether by horizontal cross-braces 22. The structural uprights 20 arecold-formed lightweight structural steel C-sections which can have anyof the general profiles shown in FIGS. 18 a to 18 j. In FIGS. 18 a to 18h, the C-section is shown either unswaged (FIG. 18 a) or with one ormore swages 23 formed in the back 20 a, side 20 b or front 20 c faces ofthe section. FIGS. 18 e, 18 f, 18 g and 18 h show how the C-sectionincludes an inturned flange 24 on each of the front faces 20 c of thesection. FIGS. 18 i and 18 j show how the C-section can be furtherreinforced by the inclusion of additional C-sections to create closedbox sections for additional strength.

For structural uprights shaped as in FIGS. 18 a to 18 j, thecross-braces 22 are of top hat section, as shown in FIG. 19, and arespot welded or plug welded to the rear of the structural uprights 20 asviewed in FIGS. 2 a to 2 d. For increased rigidity, short spacersections 26 of similar section can be positioned between adjacentstructural uprights 20, and spot welded to the cross-braces 22.

FIGS. 18 k to 18 n show how the structural uprights may have amulti-curve C-section profile as described and claimed in W068007, inwhich case the cross-braces and cross-beams may also have any of thesame general profiles.

Extending vertically down each side and end wall lattice structure andsecured to the cross-braces 22 either directly or through the spacermembers 26 are a vertical array of cold-formed steel resilient bars 28each of which has a Z-section with obtuse angles as illustrated in FIG.20.

Extending laterally from each structural upright 20 is a pair of spurmembers 30 and 32, as shown in FIGS. 8 and 7 respectively. The spurmembers 32 are of different sizes to correspond to the sizes of thecorresponding cross-beams at floor and ceiling height, but each isconstructed as shown in FIGS. 13 to 16. FIG. 13 shows a blank 34 ofsheet steel which is bent along the broken lines into the generalconformation shown in FIG. 14. That shape is then fixed againstdistortion by spot welding into position a reinforcing plate 36 as shownin FIG. 15, the lines of the spot welds being shown by a rows of crossesin FIG. 15. Finally a pair of vertical C-section channels are spotwelded along the vertical edge as shown in FIG. 16, to create a generalplan view which is T-shaped. The cross bar of the T, defined by the twoC-sections 38, is received in the recesses of the structural uprights 20in the same positions as the reinforcing C-sections 25 which are shownin FIGS. 18 i and 18 j, leaving the stem of the T jutting outtransversely as a spur 30 or 32. Onto or into each projecting spurmember 30, 32 is sleeved a cross-beam 40 of the floor or roof of themodule, as illustrated in FIG. 2 e. Reinforcing cross-members 42 may bewelded in place as required, for greater structural rigidity.

FIG. 17 shows an alternative construction for the spur members 30,32. Asingle piece of C-section channel 44 is provided with a cap 42 of tophat section, the two being welded together with spot welding or plugwelding. The top hat section 42 forms the bar of the resulting T-sectionspur member, and is received in the C-section of the structuraluprights. The C-section 40 projects as the spur.

If the structural uprights and cross-beams have the profiles of FIGS. 18k to 18 n, the spur members are connected as described in my copendingPatent Applkication No W068007.

Once the skeletal shell has been assembled as described above, it islined for example with plasterboard 44 as shown in FIGS. 3 and 4.Preferably two sheets of plasterboard 44 are used, on both the walls andthe ceiling. Flooring 46 is also added (see FIG. 4) and may be forexample plywood, chipboard or OSB panels.

The connection of the plasterboard cladding 44 to the skeletal shell isthrough the steel resilient bars 28, which are sized such as to hold theplasterboard wall panels 44 clear of the structural uprights 20 as shownin FIGS. 3 and 4. The spacing is there illustrated as being extremelysmall, but even a small spacing does establish acoustic insulationtogether with a long and convoluted heat path from the plasterboard wallpanels 44 to the structural uprights 20, as any heat resulting, forexample, from an internal fire in the finished module has to passlaterally across the resilient bars 28 to the cross-braces 22, and thenlongitudinally along those cross-braces 22 to the structural uprights20.

After the internal cladding has been secured in position as described,the building module can be completely fitted out in a factory beforebeing transported to a building site where it is lifted into positionalongside or on top of other similar modules, to create the finishedbuilding. Door and window final fittings, together with electrical andplumbing connections, are incorporated into each modular building unitbefore the unit is assembled with others as a building, then all that isnecessary is to connect in those services and finish the building with afinal facing skin which could be of brick or timber, to complete a fullyinternally decorated building.

Other details of the structure are apparent from FIGS. 9 to 12. Elementsof a doorframe 50 are shown in FIG. 9, and comprise studs consisting ofan LC-section with an insert SC-section. FIG. 10 shows a detail ofcorner studding. Structural uprights 52 are provided at the corners,each consisting of an LC-section with an inset SC-section. FIGS. 11 and12 show how a greater structural strength is obtained on an outside wallby creating the outside end wall as a sandwich of a first array ofstructural uprights 20 connected together by cross-braces 22, andattached to the outside of that a second array of structural uprights20′ connected together with cross-braces 22′. Externally, the module iscompleted with a bottom angle 54 and a top angle 56 to finish thecorners, and internally with a bottom angle 58 and a top angle 60, allas shown in FIGS. 3 and 4.

In practice, the side and end wall lattice frameworks of FIGS. 2 a to 2d are created on site in a first factory. If desired the spur membersmay be welded into position at that initial assembly site; oralternatively they may be provided to be slotted into place and weldedinto position at a second, less skilled, assembly site provided that theside and end wall lattice frameworks are provided with adequate locationmeans to enable those spur members to be placed into a fully located endposition before being welded in place. The essentially flat sections arethen transported, by road or by rail, to that second site which is aregional site where they are built up into the finished module. First ofall the two side wall latticed frameworks are connected one to the otherby means of the cross-beams 30 and 32 at floor and ceiling height. Thenthe end wall lattice frameworks are presented up and welded intoposition. Next, the internal cladding is secured in position andpreferably an additional sheet of external roof cladding is fixed overthe roof of the module. The roof cladding may for example be OSB boardof full flooring strength. Finally the interior of the module is paintedand decorated to a final desired standard, including if necessarycarpets and general fixtures such as fixed cupboards, before thefinished module is moved from the second assembly site to the finalbuilding site.

Stacking of adjacent modules, and securing them together, is asdescribed and claimed in my other three Patent Applications, W068005,W068006 and W068007, filed herewith. The modules as already describedmay be stacked and assembled into buildings up to twenty storeys highHowever to construct taller buildings, or buildings which are subject tosevere lateral stresses by virtue of either their location in a windyenvironment or their tall narrow geometry, it may be desirable tostrengthen the outside walls using diagonal cross-braces orcompression-resistant columns. The compression-resistant columns may bebuilt into the walls of the pre-formed rectangular frame units, or maybe secured to the outside of the individual modules or stacks ofmodules. In the former case the structural uprights would be made thesame height as the individual walls of the building units; in the lattercase they might be the height of a single storey of the building or theheight of two or more storeys. FIG. 21 illustrates one form ofcompression-resistant column made by filling a tubular metal column 62with concrete 63. The steel upright 62 may be formed from lightweightcold-formed steel section. The concrete fill 63 is formed into a domednib 64 at the top, with a corresponding domed indent 65 at the bottom.When the resulting columns are placed one above the other to provideouter reinforcement for the finished building, then the nib 64 of eachcolumn engages in the corresponding recess 65 of the correspondingcolumn of the storey immediately above, for positive location. FIG. 21also shows the provision of steel reinforcing bars 66 which add morestructural strength to the compression resistant columns. If the columnsare not built into the walls of the individual modules, then they may besecured to the outside walls, for example by welding.

FIG. 22 shows how the compression-resistant columns may be built intothe wall lattice framework. A pre-cast column 71 of reinforced concreteis provided, to extend the height of the wall lattice framework. The topand bottom may be provided with a nib and indent corresponding to thosenumbered 64 and 65 in FIG. 21. The column 70 is shaped to lie betweentwo structural uprights 20 each having the profile shown in FIG. 18 n,and steel straps 71 are welded to the outside of the uprights 20 to holdthe assembly together. That reinforced composite structural upright maythen be assembled into a wall lattice framework as described elsewherein this specification.

FIG. 23 illustrates a highly preferred wall lattice framework forincorporation into a building module according to the invention. Thestructural uprights 20 and cross-braces 22 have the profile of any ofFIGS. 18 k to 18 n. The cross-braces 22 are connected diagonally, in atriangulation pattern for maximum strength. Each cross-brace 22 isconnected to its associated structural uprights 20 and to the adjacentcross-brace 22 by a pair of pressed steel plates 72 positioned one onthe outsid eand one on the inside of the wall lattice framework andwelded to the uprights 20 and cross-braces 22. Chain-dotted lines 73indicate the lines of connection of the steel resilient bars 28.

The individual building modules made up as described need not berectangular in plan view. Any plan shape can be accommodated.Trapezoidal modules can be places together to create either straight orcurved buildings. The modules can include features such as balconies tolie on the outside wall of the finished building. The walls do not evenhave to be straight, as it can be appreciated from FIG. 23 that a curvedwall can easily be constructed, for use according to this invention,from the multi-curve C-section profiled structural uprights andcross-braces of my Patent Application No W068007.

1. A modular building unit comprising a shell formed from side walllattice frameworks connected together by cross-beams at floor andceiling height and end wall lattice frameworks secured to the ends ofthe resulting structure, wherein each of the wall lattice frameworkscomprises an array of mutually parallel spaced structural uprights madefrom cold-formed structural steel sections, secured together byhorizontal or diagonal cross-braces also made from cold-formedstructural steel sections, each of the cross-beams is made from acold-formed structural steel C-section and is connected to the walllattice frameworks by being sleeved into or around lateral spur membersextending from the wall lattice frameworks prior to being weldedthereto, the cross-braces of each wall lattice framework are centred ona plane that is displaced outwardly from the internal dimensions of theshell, and internal cladding on the interior of the shell comprises wallpanels connected to the cross-braces by cold-formed steel resilient barseach of which has one longitudinal edge portion secured to thecross-braces and an opposite longitudinal edge portion secured to thewall panels to hold the wall panels out of contact with the structuraluprights and to define an extended heat path from the wall panels to thestructural uprights through the resilient bars and through alongitudinally extending portion of each cross-brace.
 2. A modularbuilding unit according to claim 1, wherein the structural uprights areof C-section and the spur members are T-shaped or L-shaped eachcomprising two limbs of which one sits inside the C-section of theassociated structural upright and the other extends transverselytherefrom as a spur to receive an end of an associated cross-beam.
 3. Amodular building unit according to claim 2, wherein each limb of thespur member is made of cold-formed structural steel and has a generalC-section.
 4. A modular building unit according to any preceding claim,wherein each C-section includes one or more swages in the back, side orfront faces of the section.
 5. A modular building unit according to anypreceding claim, wherein each C-section includes an inturned flange onone or both of the front elements of the section.
 6. A modular buildingunit according to any preceding claim, wherein in each wall panel thecross-braces are welded to the outsides of the structural uprights.
 7. Amodular building unit according to any of claims 1 to 5, wherein in eachwall panel the cross-braces pass through slots formed in the structuraluprights.
 8. A modular building unit according to claim 7, wherein theslots are created by stamping apertures in the steel stock from whichthe structural uprights are formed, prior to cold-forming the steelstock into the sectional profile of the structural uprights.
 9. Amodular building unit according to claim 1, wherein the structuraluprights, the cross-beams and the cross-braces are all formed fromcold-rolled structural steel sections comprising a pair of arcuate orsubstantially arcuate opposite side portions each of which extends in awholly or substantially smooth arc from a central slot opening onto thecorresponding lateral side and from the corresponding lateral side ontoan arcuate or substantially arcuate concave portion of a rear wall. 10.A modular building unit according to claim 8, wherein the cross-bracesare connected in the plane of the structural uprights and extenddiagonally from one structural upright to the next.
 11. A modularbuilding unit according to claim 8 or claim 9, wherein selectedstructural uprights and/or selected cross-beams are reinforced byincluding, within one or both of the arcuate or substantially arcuateopposite side portions, a reinforcing rod or tube.
 12. A modularbuilding unit according to claim 11, wherein the ends of the reinforcingrods or tubes are provided with connecting means for connecting them tothe reinforcing rods or tubes of adjacent modules, to connect togetherthe modules.
 13. A modular building unit according to any precedingclaim, wherein additional floor panel thickness external panels aresecured over the top of the shell.
 14. A modular building unit accordingto any preceding claim, wherein each of the connections between thestructural uprights and the horizontal cross-braces and each of theconnections between the spur members and the structural uprights and thecross-beams incorporates at least one weld that is a spot weld, a seamweld or a plug weld.
 15. A modular building unit according to anypreceding claim, wherein door and window final fittings, together withelectrical and plumbing connections, are incorporated into the modularbuilding unit before that unit is assembled with others as a building.16. A method of fabricating a modular building unit according to anypreceding claim, comprising: (a) creating a shell by: (i) fabricatingthe wall lattice frameworks each comprising: an array of mutuallyparallel spaced structural uprights secured together by horizontal ordiagonal cross-braces, both the structural uprights and the cross-bracesbeing made from cold-formed structural steel sections, with thecross-braces being centred on a plane that is displaced outwardly fromthe internal dimensions of the shell, and a row of floor level spurmembers and a row of ceiling level spur members extending laterally fromthe structural uprights of each wall lattice framework; (ii) joiningtogether the wall lattice frameworks to form the shell by sleeving thecross-beams of cold-formed structural steel C-section into or around thespur members and then welding the cross-beams to the spur members; and(iii) securing the end wall lattice frameworks to opposite ends of theshell so formed; and (b) lining the shell by securing the wall panels tothe cross-braces by securing one longitudinal edge portion of each of anarray of cold-formed steel resilient bars to the cross-braces and anopposite longitudinal edge portion of each of the resilient bars to thewall panels to hold the wall panels out of contact with the structuraluprights and to define an extended heat path from the wall panels to thestructural uprights through the resilient bars and through alongitudinally extending portion of each cross-brace.
 17. A methodaccording to claim 12, wherein the side and end wall lattice frameworksare made and assembled at a first manufacturing site; those assembledframeworks are transported to a second manufacturing site; the walllattice frameworks are assembled with the cross-beams to form the shellat the second manufacturing site; and the shell is lined and fitted-outat the second manufacturing site.